Lecture 25 Flashcards
What are the two excessively simplified groups that fungi can be typed into?
Yeasts which are round or oval and reproduce via budding
Moulds which have tubular hyphae and reproduce via spores
What are the two types of pathogenic yeasts?
Candida Albicans which is the typical cause of almost all fungal disease and cryptococcus neoformans which very rarely causes disease and is encased in a sugar capsule
What are the three pathogenic moulds?
Dermatophytes that is the most common cause of mould diseases
Aspergillus species which only very rarely cause disease in patients with a very low neutrophil count
Zygomycetes
Where is candida albicans typically found and how does it induce disease?
It is a commensal of the mouth, gut and vagina however overgrowth which can occur due to suppression of the immune system or its neighboring non-pathogenic bacteria
How does canidida albicans appear in labs?
Black yeasts with pseudohyphae in the gram stain
Will appear as larger than bacteria
Grows well on blood agar
What are the 4 different conditions that can occur as a result of candida albicans overgrowth?
Overgrowth typicaly occurs in warm moist areas Pharyngitis via growth in the oesophagus Vaginitis via growth in the vagina Intertrigo via growth in the armpit Candid vulvovaginitis or nappy rash
Is overgrowth of candida albicans invasive?
No as it does not invade into tissues of the blood
How is overgrowth of candida albicans treated?
Typically topical through
nystatin suspension or pastiles,
amphotericin B pastilles,
azole pessaries or cream (for vaginal infections)
What are the two types of cryptococcus neoformans?
C.neoformans var neoformans which is associated with pigeon faeces
C.neoformans var gatti
associated with eucalyptus trees
What type of disease is caused by c.neoformans?
Typically an asymptomatic pulmonary infection, although in severly immunocompromised patients disease can progress to meningitis
How is meningitis caused by c.neoformans detected and then treated?
DIagnosis by detection of antigen, microscopy or culture
Treatment is via amphotericin B IV or oral fluconazole
What type of disease do dermatophytes cause?
Tinea or ringworm which is never invasive
What are the three dermatophytes which cause tinea?
Microsporum species
Trichophyton species
Epidermophyton species
How can tinea supppurans appear to cause baldness?
Mould growth occurs in hair follicle, which odes not kill th hair but makes it very brittle so it easily breaks off
What is onchomycosis?
Tinea of the nailbed
How are dermatophyte infections treated?
A topical azole is used for most infections
Although nails require an oral azole to be used as the infection site is inaccessible
What are two common skin infections caused by dermatophytes not including tinea?
Pityriasis versicolor caused by malassezia furfur, this appears as hypopigmented macules on the trunk and is treated with azoles
Seborrheic dermatitis caused by pityrosporum species which cause a greasy facial rash and dandruff these are also treated with topical azole
What is aspergillus fumigatus?
A spore bearing branched mould typically found in rotting vegetation
This is a disease which only causes disease in those who are neutropenic
Can also cause allergic bronchopulmonary aspergillosis
What is neutropenic?
A deficiency of neutrophils
What is allergic bronchopulmonary aspergillosis?
Damage to the lungs allows build up of mucus which allows growth of aspergillus fumigatus
What occurs with aspergillus fumigatus?
Cavitating pneumonia
How is aspergillus fumigatus diagnosed?
Microscopy and culture
How is aspergillus fumigatus treated?
Amphotericin B IV for weeks
Liposomal amphotericin B
Voriconazole and other azoles
Surgery
How does amphotericin B function as an antifungal drug?
Binds to ergosterol which is not found in humans allowing disruption of targeted cytoplasmic membranes
Its infusion is rleated with anaphylatic reactions
has nephrotoxicity due to K+ loss
lipid versions (liposomal) are less topic
What is the IV dosage of amphotericin B?
0.5-1g/Kg
How do azoles function as an antifungal drug?
Inhibition of ergosterol synthesis
Typically given through IV and is a relatively non toxic antifungal drug
